802.11b with a data-transfer speed of 11 megabits per second.
802.11g at 54Mbps
802.11n top speed of 450Mbps [NOW]
802.11ac at 1 gigabit per second [about Dec 2012] uses 5 GHz spectrum, coverage range of a house or with antennas similar to earlier wifi
802.11ad at 7 Gbps. [about Dec 2012] uses 60 GHz spectrum, range of coverage about one room. With antennas can get farther but tougher to get more range.

60 GHz spectrum is faster but the signals are stopped by water, by air, by walls.